static gboolean test_dvb_s2_crc(tvbuff_t *tvb, guint offset) {
guint8 input8;
/* only check BB Header and return */
if (tvb_captured_length(tvb) < (offset + DVB_S2_BB_HEADER_LEN))
return FALSE;
input8 = tvb_get_guint8(tvb, offset + DVB_S2_BB_OFFS_CRC);
if (compute_crc8(tvb, DVB_S2_BB_HEADER_LEN - 1, offset) != input8)
return FALSE;
else
return TRUE;
}
static int
verify_header_crc8(headerrev_t head_ver, unsigned char *bytes, int length)
{
int crc_offset = 0;
unsigned char orig_crc8 = 0;
unsigned char calc_crc8 = 0;
switch (head_ver) {
case SECTION_HDR_VER:
crc_offset = 4;
break;
default:
errno = EINVAL;
return (0);
}
orig_crc8 = bytes[crc_offset];
bytes[crc_offset] = 0x00; /* clear for calc */
calc_crc8 = compute_crc8(bytes, length);
bytes[crc_offset] = orig_crc8; /* restore */
return (orig_crc8 == calc_crc8);
}
static int dissect_dvb_s2_bb(tvbuff_t *tvb, int cur_off, proto_tree *tree, packet_info *pinfo)
{
proto_item *ti;
proto_tree *dvb_s2_bb_tree;
guint8 input8, matype1;
guint16 input16, bb_data_len = 0, user_packet_length;
int sub_dissected = 0, flag_is_ms = 0, new_off = 0;
static const int * bb_header_bitfields[] = {
&hf_dvb_s2_bb_matype1_gs,
&hf_dvb_s2_bb_matype1_mis,
&hf_dvb_s2_bb_matype1_acm,
&hf_dvb_s2_bb_matype1_issyi,
&hf_dvb_s2_bb_matype1_npd,
&hf_dvb_s2_bb_matype1_ro,
NULL
};
col_append_str(pinfo->cinfo, COL_PROTOCOL, "BB ");
col_append_str(pinfo->cinfo, COL_INFO, "Baseband ");
/* create display subtree for the protocol */
ti = proto_tree_add_item(tree, proto_dvb_s2_bb, tvb, cur_off, DVB_S2_BB_HEADER_LEN, ENC_NA);
dvb_s2_bb_tree = proto_item_add_subtree(ti, ett_dvb_s2_bb);
matype1 = tvb_get_guint8(tvb, cur_off + DVB_S2_BB_OFFS_MATYPE1);
new_off += 1;
if (BIT_IS_CLEAR(matype1, DVB_S2_BB_MIS_POS))
flag_is_ms = 1;
proto_tree_add_bitmask_with_flags(dvb_s2_bb_tree, tvb, cur_off + DVB_S2_BB_OFFS_MATYPE1, hf_dvb_s2_bb_matype1,
ett_dvb_s2_bb_matype1, bb_header_bitfields, ENC_BIG_ENDIAN, BMT_NO_FLAGS);
input8 = tvb_get_guint8(tvb, cur_off + DVB_S2_BB_OFFS_MATYPE2);
new_off += 1;
if (flag_is_ms) {
proto_tree_add_uint_format_value(dvb_s2_bb_tree, hf_dvb_s2_bb_matype2, tvb,
cur_off + DVB_S2_BB_OFFS_MATYPE2, 1, input8, "Input Stream Identifier (ISI): %d",
input8);
} else {
proto_tree_add_uint_format_value(dvb_s2_bb_tree, hf_dvb_s2_bb_matype2, tvb,
cur_off + DVB_S2_BB_OFFS_MATYPE2, 1, input8, "reserved");
}
user_packet_length = input16 = tvb_get_ntohs(tvb, cur_off + DVB_S2_BB_OFFS_UPL);
new_off += 2;
proto_tree_add_uint_format(dvb_s2_bb_tree, hf_dvb_s2_bb_upl, tvb,
cur_off + DVB_S2_BB_OFFS_UPL, 2, input16, "User Packet Length: %d bits (%d bytes)",
(guint16) input16, (guint16) input16 / 8);
bb_data_len = input16 = tvb_get_ntohs(tvb, cur_off + DVB_S2_BB_OFFS_DFL);
bb_data_len /= 8;
new_off += 2;
proto_tree_add_uint_format_value(dvb_s2_bb_tree, hf_dvb_s2_bb_dfl, tvb,
cur_off + DVB_S2_BB_OFFS_DFL, 2, input16, "%d bits (%d bytes)", input16, input16 / 8);
new_off += 1;
proto_tree_add_item(dvb_s2_bb_tree, hf_dvb_s2_bb_sync, tvb, cur_off + DVB_S2_BB_OFFS_SYNC, 1, ENC_BIG_ENDIAN);
new_off += 2;
proto_tree_add_item(dvb_s2_bb_tree, hf_dvb_s2_bb_syncd, tvb, cur_off + DVB_S2_BB_OFFS_SYNCD, 2, ENC_BIG_ENDIAN);
new_off += 1;
proto_tree_add_checksum(dvb_s2_bb_tree, tvb, cur_off + DVB_S2_BB_OFFS_CRC, hf_dvb_s2_bb_crc, hf_dvb_s2_bb_crc_status, &ei_dvb_s2_bb_crc, pinfo,
compute_crc8(tvb, DVB_S2_BB_HEADER_LEN - 1, cur_off), ENC_NA, PROTO_CHECKSUM_VERIFY);
switch (matype1 & DVB_S2_BB_TSGS_MASK) {
case DVB_S2_BB_TSGS_GENERIC_CONTINUOUS:
/* Check GSE constraints on the BB header per 9.2.1 of ETSI TS 102 771 */
if (BIT_IS_SET(matype1, DVB_S2_BB_ISSYI_POS)) {
expert_add_info(pinfo, ti, &ei_dvb_s2_bb_issy_invalid);
}
if (BIT_IS_SET(matype1, DVB_S2_BB_NPD_POS)) {
expert_add_info(pinfo, ti, &ei_dvb_s2_bb_npd_invalid);
}
if (user_packet_length != 0x0000) {
expert_add_info_format(pinfo, ti, &ei_dvb_s2_bb_upl_invalid,
"UPL is 0x%04x. It must be 0x0000 for GSE packets.", user_packet_length);
}
while (bb_data_len) {
/* start DVB-GSE dissector */
sub_dissected = dissect_dvb_s2_gse(tvb, cur_off + new_off, tree, pinfo, bb_data_len);
new_off += sub_dissected;
if ((sub_dissected <= bb_data_len) && (sub_dissected >= DVB_S2_GSE_MINSIZE)) {
bb_data_len -= sub_dissected;
if (bb_data_len < DVB_S2_GSE_MINSIZE)
bb_data_len = 0;
} else {
bb_data_len = 0;
}
}
break;
case DVB_S2_BB_TSGS_GENERIC_PACKETIZED:
proto_tree_add_item(tree, hf_dvb_s2_bb_packetized, tvb, cur_off + new_off, bb_data_len, ENC_NA);
new_off += bb_data_len;
break;
case DVB_S2_BB_TSGS_TRANSPORT_STREAM:
proto_tree_add_item(tree, hf_dvb_s2_bb_transport, tvb, cur_off + new_off, bb_data_len, ENC_NA);
new_off += bb_data_len;
break;
default:
proto_tree_add_item(tree, hf_dvb_s2_bb_reserved, tvb, cur_off + new_off,bb_data_len, ENC_NA);
new_off += bb_data_len;
expert_add_info(pinfo, ti, &ei_dvb_s2_bb_reserved);
break;
}
return new_off;
}
